Replace Column layout with Box+manual y-offset for collapse animation

Switch CalendarMonthPage from Column to Box with calculated y positions per row,
enabling precise height computation that aligns with CalendarMonthView's
BottomCard positioning. Simplify cardTopPx calculation by deriving grid height
from the same formula instead of tracking expandedCalendarHeightPx separately.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

shared/src/commonMain/kotlin/plus/rua/project/ui/CalendarMonthPage.kt

@@ -1,6 +1,6 @@
 package plus.rua.project.ui
 
-import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.height
@@ -42,37 +42,68 @@ fun CalendarMonthPage(
         weeks.indexOfFirst { week -> week.any { it.date == selectedDate } }
     }
 
+    val hasSelectedWeek = selectedWeekIndex >= 0
+
     var rowHeightPx by remember { mutableIntStateOf(0) }
     val rowMeasured = rowHeightPx > 0
+    val H = rowHeightPx.toFloat()
 
-    // 选中行上移距离 = 上方行数 × 行高 × progress
+    // 总高度 = 6行 × 行高（展开时），或选中行高度（折叠时）
-    val selectedOffsetPx = if (rowMeasured) {
+    val totalHeightDp = if (rowMeasured) {
-        -(selectedWeekIndex.toFloat() * rowHeightPx.toFloat() * collapseProgress)
+        if (hasSelectedWeek) {
+            // 选中行高度 + 上方行压缩高度 + 下方行压缩高度
+            val aboveH = selectedWeekIndex * H * (1f - collapseProgress)
+            val belowH = (weeks.size - 1 - selectedWeekIndex) * H * (1f - collapseProgress)
+            val selH = H
+            with(density) { (aboveH + selH + belowH).toDp() }
+        } else {
+            with(density) { (weeks.size * H).toDp() }
+        }
     } else {
-        0f
+        null
     }
-    val selectedOffsetDp = with(density) { selectedOffsetPx.toDp() }
 
-    Column(modifier = modifier.clipToBounds()) {
+    Box(modifier = modifier.clipToBounds().then(
+        if (totalHeightDp != null) Modifier.height(totalHeightDp)
+        else Modifier
+    ).onSizeChanged { size ->
+        if (collapseProgress > 0f) {
+            println("[Page] totalH=${size.height}px p=$collapseProgress selWeek=$selectedWeekIndex rowH=$rowHeightPx")
+        }
+    }) {
         weeks.forEachIndexed { weekIndex, week ->
-            val isSelected = weekIndex == selectedWeekIndex
+            val isSelected = hasSelectedWeek && weekIndex == selectedWeekIndex
-            val isAboveSelected = weekIndex < selectedWeekIndex
+            val isAbove = hasSelectedWeek && weekIndex < selectedWeekIndex
-            val isBelowSelected = weekIndex > selectedWeekIndex
+            val isBelow = hasSelectedWeek && weekIndex > selectedWeekIndex
 
-            // 非选中行高度跟手压缩
             val rowScale = when {
-                isAboveSelected || isBelowSelected -> 1f - collapseProgress
+                isAbove || isBelow -> 1f - collapseProgress
                 else -> 1f
             }
 
             val rowHeightDp = if (rowMeasured && rowScale > 0.01f) {
-                with(density) { (rowHeightPx.toFloat() * rowScale).toDp() }
+                with(density) { (H * rowScale).toDp() }
             } else if (!rowMeasured) {
                 null
             } else {
                 0.dp
             }
 
+            // 手动计算每行的视觉 y 位置
+            val yOffsetDp = if (rowMeasured && hasSelectedWeek) {
+                val yPx = when {
+                    isAbove -> weekIndex * H * (1f - collapseProgress)
+                    isSelected -> selectedWeekIndex * H * (1f - collapseProgress)
+                    isBelow -> selectedWeekIndex * H * (1f - collapseProgress) + H + (weekIndex - selectedWeekIndex - 1) * H * (1f - collapseProgress)
+                    else -> weekIndex * H
+                }
+                with(density) { yPx.toDp() }
+            } else if (rowMeasured) {
+                with(density) { (weekIndex * H).toDp() }
+            } else {
+                0.dp
+            }
+
             val shouldShow = rowHeightDp == null || rowHeightDp > 0.dp
 
             if (shouldShow) {
@@ -84,10 +115,7 @@ fun CalendarMonthPage(
                             if (rowHeightDp != null) Modifier.height(rowHeightDp)
                             else Modifier
                         )
-                        .then(
+                        .offset(y = yOffsetDp)
-                            if (isSelected && rowMeasured) Modifier.offset(y = selectedOffsetDp)
-                            else Modifier
-                        )
                         .onSizeChanged { size ->
                             if (size.height > 0 && !rowMeasured) {
                                 rowHeightPx = size.height

shared/src/commonMain/kotlin/plus/rua/project/ui/CalendarMonthView.kt

@@ -5,7 +5,6 @@ import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.height
-import androidx.compose.foundation.layout.offset
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.statusBarsPadding
 import androidx.compose.runtime.Composable
@@ -19,7 +18,6 @@ import androidx.compose.ui.Modifier
 import androidx.compose.ui.layout.onSizeChanged
 import androidx.compose.ui.platform.LocalDensity
 import androidx.compose.ui.unit.dp
-import kotlinx.datetime.LocalDate
 import kotlinx.datetime.TimeZone
 import kotlinx.datetime.todayIn
 import kotlin.time.Clock
@@ -44,26 +42,34 @@ fun CalendarMonthView(
     val density = LocalDensity.current
 
     var calendarHeightPx by remember { mutableIntStateOf(0) }
-    var screenHeightPx by remember { mutableIntStateOf(0) }
-    var expandedCalendarHeightPx by remember { mutableIntStateOf(0) }
     var monthHeaderHeightPx by remember { mutableIntStateOf(0) }
     var weekdayHeaderHeightPx by remember { mutableIntStateOf(0) }
+    var screenHeightPx by remember { mutableIntStateOf(0) }
 
-    // 日历网格高度 = 总高度 - MonthHeader - WeekdayHeader
+    val p = viewModel.collapseProgress
-    val expandedGridHeightPx = expandedCalendarHeightPx - monthHeaderHeightPx - weekdayHeaderHeightPx
+    val headerHeightPx = monthHeaderHeightPx + weekdayHeaderHeightPx
-    // 折叠偏移量 = 进度 × 网格5行高度（保留1行可见）
+
-    val collapseOffsetPx = if (viewModel.isCollapsed) {
+    // 展开时网格高度 = 首次测量的日历总高度 - headers
-        0
+    val expandedGridHeightPx = calendarHeightPx - headerHeightPx
-    } else {
+    val weeksCount = 6
-        -(viewModel.collapseProgress * expandedGridHeightPx * 5f / 6f).toInt()
+
-    }
+    // 折叠时网格高度公式（与 CalendarMonthPage 一致）：
-    val cardTopPx = if (viewModel.isCollapsed) {
+    // gridH = rowH × (1 + (weeks-1) × (1-p))
-        calendarHeightPx
+    // 其中 rowH = expandedGridHeightPx / weeksCount
-    } else {
+    val gridHeightPx = if (expandedGridHeightPx > 0 && p > 0f) {
-        expandedCalendarHeightPx + collapseOffsetPx
+        val rowH = expandedGridHeightPx.toFloat() / weeksCount
-    }
+        (rowH * (1 + (weeksCount - 1) * (1f - p))).toInt()
+    } else if (expandedGridHeightPx > 0) {
+        expandedGridHeightPx
+    } else 0
+
+    val cardTopPx = headerHeightPx + gridHeightPx
     val cardHeightPx = screenHeightPx - cardTopPx
 
+    if (p > 0f) {
+        println("[View] p=$p monthH=$monthHeaderHeightPx weekdayH=$weekdayHeaderHeightPx expandedGridH=$expandedGridHeightPx gridH=$gridHeightPx cardTop=$cardTopPx cardH=$cardHeightPx screenH=$screenHeightPx calH=$calendarHeightPx isCollapsed=${viewModel.isCollapsed}")
+    }
+
     Box(
         modifier = modifier
             .fillMaxSize()
@@ -73,12 +79,11 @@ fun CalendarMonthView(
             }
     ) {
         Column(modifier = Modifier.padding(horizontal = 16.dp).onSizeChanged { size ->
-            calendarHeightPx = size.height
+                // 仅在展开时记录日历总高度（折叠时 HorizontalPager 不缩小）
-            // 仅在首次展开时记录完整日历高度，折叠后不再覆盖
+                if (p < 0.01f) {
-            if (!viewModel.isCollapsed && viewModel.collapseProgress < 0.01f) {
+                    calendarHeightPx = size.height
-                expandedCalendarHeightPx = size.height
+                }
-            }
+            }) {
-        }) {
             MonthHeader(
                 year = currentYear,
                 month = currentMonth,